ix years after Big Dig contractors received design drawings so flawed that they failed to include the FleetCenter, the Massachusetts Turnpike Authority has directed its legal team to pursue a refund from the Big Dig's managers, Bechtel/Parsons Brinckerhoff, for the mistake.

The FleetCenter case, which has come to symbolize the problems plaguing the $14.6 billion project and the state's failure to protect taxpayers, is one of six cost-recovery items now receiving legal scrutiny by the Turnpike Authority. The cases were opened, Turnpike Authority chairman Matthew Amorello said, in response to a Globe investigation that described a series of design and management mistakes committed by Bechtel.

"It's a disturbing matter that needs to be reviewed," Amorello said in a statement, in reference to the FleetCenter mistake.

The Turnpike Authority's lawyers will also focus their attentions on these cases:

* A disastrous flood that took place in September 2001 at the Fort Point Channel tunnel. Documents showed that Bechtel engineers noted flaws with the area two years before, yet failed to order repairs.

* A design conflict near the North End between a Central Artery tunnel ramp and the Green Line. Documents showed that MBTA officials warned Bechtel about the problem well before construction began, but the warning was either forgotten or ignored.

* A design conflict at the Ted Williams Tunnel that resulted in the tunnel tubes being too short to meet.

In the FleetCenter case, the Globe investigation found that Bechtel's preliminary designs failed to include the 19,600-seat arena, even though the building was nearly complete when they handed their drawings to a smaller firm to finish. Then, Bechtel failed to make sure the building was depicted on drawings when it allowed construction to commence in 1997, two years after the FleetCenter had opened. The investigation found overruns totalling $991,000 tied to the gaffe.

All told, the Globe investigation tied about $1.1 billion in construction cost overruns to mistakes and poor decisions made by Bechtel, which created the project's basic design and managed every aspect of the Big Dig.

In a letter to the Globe's editors, Bechtel project director C. Matthew Wiley said the missing FleetCenter mistake was not Bechtel's fault, but that of the design firm that Bechtel supervised. He also said the problem cost just $30,000.

"This kind of hyperbole and untruth is deeply unfair," Wiley said. "The Globe still fails to grasp fundamentals of the engineering-and-construction industry."

Wiley's letter did not explain why Bechtel managers never pointed out the problem for potential cost-recovery against the firm it supervised, even though that was one of Bechtel's duties.

Bechtel's spokesman did not return a message.

Big Dig chief counsel Kurt Dettman, who runs the project's cost-recovery efforts, said the state will vigorously pursue a refund for the FleetCenter and other mistakes, but the effort will take some time.

"Obviously, this doesn't happen overnight," he said. "It's referred to our outside engineering firm. They gather documents, interview the knowledgeable people, and issue a report that is then referred to the lawyers, which is yours truly."

Dettman said the effort to recover money would be made far easier if a bill passed in the Senate on Thursday becomes law.

The bill, which is likely to be voted on in the House in the next two weeks, would extend the statute of limitations for filing legal claims for management mistakes to 10 years past the end of the Big Dig, which is scheduled to wrap up in 2005. Current laws allow cases to be commenced just six years past the time the mistake was discovered.

Asked why the Big Dig had never opened cost-recovery cases on the problems cited in the Globe, Dettman said some were already the focus of such efforts, but added, "I'm not taking any chances."

"We want to cast a wide net just in case," Dettman said.

To date, only 3 percent of Big Dig overruns have been the subject of cost-recovery efforts. In its 12-year history, the Big Dig has opened just 371 cases, including the new ones. There have been nearly 12,000 construction cost overruns, totalling more than $1.6 billion.

Bechtel has never paid money back to the state for its mistakes. In 2001, the company offered to take $50 million off of its fee, but the offer was only good if Bechtel was given far more control over project spending.

Turnpike Authority officials declined the offer.

Raphael Lewis can be reached at rlewis@globe.com. The Globe's series, entitled "Easy Pass: Why Bechtel never paid for its Big Dig mistakes," can be found at www.boston.com/bechtel.